Clamshell dredge



A. w. ROBINSON CLAMS HELL DREDGE 3 Sheets-Sheet 1 Filed Feb. 19, 1924 gum/4 601 llllllllllllll J i l |||L w lllilllllu .E ii a M M P -L Aug. 11; 1925.

A. w. RoBmisoN CLAMSHELL DREDG'E 7 Filed Feb. 19, 192

3 heets-Sheet 2 11 ill Aug. 11, 1925.

A. W. RO BINSON CLAMSHELL DREDGE Filed Feb. 19, 1924 s Sheets-Sheet 5 a waukoz Patented Aug- 11:, 19258 IUNITE S S- uman wmmsnonmson, or UPPER moumzni Queens, cannon.

1 manner. DBEDGE.

Application filed February 19, 1924. Serial 110. 093,740.

To all whom it may concern Be it known that I, ARTHUR WELLS ROBIN-' soN, a citizen of the Dominionof Canada,

or into a barge.

and'a resident of UpperMelbourne, county of Richmond, Province of Quebec, Dominion of Canada, have invented certain new and useful Improvements in Clamshell Dredges, of which the following is a specification, reference being had to the accompanying drawings.

This invention pertains to that class of dredge, in which a grab or clamshell bucket is employed. The bucket is caused to drop in an open position on'the' surface to be excavated, then close and lift, the material is deposited to one side, either on the land The invention relates more particularly to the means for hoistingand owering the bucket and of revolving or swinging it for the purpose of deposit. Alsofor opening and closing the bucket.

The ordinary and well known method of raising and lowering the clamshell bucket, is by means of suitable hoisting tackle attached to the boom ofa crane or derrick.

The bucket is freely suspended from the end of such boom,-'and a swinging or slewing motion imparted to the boom, so that the bucket may deposit its load in the required place. This method is subject to several disabilities, among which may be mentioned the tendency of the bucket to cant or topple over when-it strikes the bottom, owing to the fact that it is suspended by a flexible hoisting tackle. This is especially noticeable when the bottom is uneven, as is nearly always the case.

lit is also always diificult to cause the bucket to land in the proper-spot when danglin freely on a long tackle from the end of t e boom. Furthermore all such apparatus is necessarily unbalanced, so that the energy expended in hoisting the dead load of the bucket and its parts is Wasted on each lift, and the only useful work done, s that of lifting the dredged material.

Furthermore the energy thus expended inhoisting the bucket, is not only wasted, but

reappears in causing considerable wear of the brake bands and other arrangements that are necessary for its control when lowering.

In my invention I do not employ the usual apparatus, but substltute therefor a rolling cantilever boom, havin perfect balance of parts, and to the end of which the clamshell bucket is connected preferably by a rigid lowered but also pushed into or against the bottom for excavating purposes when lowered. c I

From this construction a number of advantages result, some of which are as follows:

(I) A- positive thrust for digging penetration of the bucket, so that harder material can be excavatedthan' would otherwise be possible. f

I (2) Balance of the parts, so that little if any lost work is expended in lifting the dead load of the bucket.

' (3) Balanced also for revolving .load, so

member, so-that it can not only be raised or i that the hullof the dredge does not list or roll, when the boom and bucket swings to oneside. v e

(4:) Boom balanced in mid-position, so that the power applied to raise or lower it is stored up and used to 'start the return stroke.

' v (9) Clamshell buc st of improved design,

having nosheaves or shafts, and working parts projecting into the mud. Ample room or mud to pile up.

. (10). Direct power closing cylinder for bucket, which opens by gravity.

(11) Bucket cannot twist or topple over as when dangling lay-ordinary hoist.

(12 Ease of operation, 3 levers only require 1 rolling, 1 closing and dumping, and one swinging.

13 Economy of fuel. y 14 Few working parts consequently lesscost of maintenance.-

Certain elementary forms in which my invention may be embodied, are shown in the accompanying drawings. They are however, by no means the only constructions ltlil of one form of a complete dredge. Fig. 2 is a plan of the same. Fig. 3 is an end view,

in which the boom with its rolling platform is shown in section. Fig. 4 is a side view of 'the clamshell bucket attached to the boom in an open position. Fig. 5 is a front view of one form of clamshell bucket attached to the end of the boom. Fig. 6 is a side view of the bucket somewhat enlarged. Fig. 7 is plan of the same, and Fig. 8 is a front view of the same. Fig. 9 is a detail section vie of the track and coasting parts.

In the drawings, 1 represents the scow float, 2 represents the cantilever boom, or rolling member. This rolling member is composed of two steel girders of curved girders of the cantilever with sufficient space between to clear the cylinder 15.

The under sides or tread of the girders in the central part 'of the boom, forms an arc of a circle as at 5. The curved portion of the boom where it rolls upon the base is formed of'greatstrength, and with a flange 6 on each side similar to the tire of a locomotive drivingwheel, so that it can roll on a -corresponding horizontal steel track 7. In order to prevent horizontal displacement of the rolling portion a portion of the track. 7 andthe trend 5 is formed with teeth or cogs -8 which engage with each other after the manner of. a rack and pinion. .9 is a circular revolving" platform across the top of which the two steel tracks 7 are laid upon which the Y girders may roll. 10 is an annular roller bearing interposedbetween the'revolving platform 9 and the hull, of the vessel. This roller bearing consists of a series of rollers 11 retained in slewingthe booms o 'placeby a ring 12, and provided with a circular track both on the under side of the platform'and on the deck of'the dredge.

e usual center pivot or hearing not shown is provided to prevent horizontal displacement, and this part of the apparatus is or may be similar in principle and con struction to that used in railway turntables, revolving bri revolving steam shovels, draglines and t 'e' like.

Rotary motion is imparted to the platform 9 by means ofa wire rope swinging gear attached thereto, consistingof reversible winding engines 13, and the guide sheaves 14. The construction of which isor may be'similar to that emfployed in swin or dredges and err cks.

ground, and causin close materlal within them, while the thrust. or

carry the cylinder in preferred position' The piston rod 17 of the cylinder terminates in a crosshead 19 which is attached to a wrist pin 20 secured to the girders 2+2 of the cantilever boom, and the position 'of which is preferably exactly in the center of the flange or arc on which the boom rolls."

'It is manifest therefore that as the rolling action takes place this wrist-pin will travel in a horizontal line, which is also the center line ofthe cylinder and piston, and that therefore no guides or connecting rods are necessary. 2121 are the two leaves or shells of a clamshell bucket, which may be of any preferred or usual construction. The shells are connected to a head 22, by four connecting links 23'. The head 22 is attached to the end of a rigid member 24, by which the whole apparatus is suspended from the end of the boom.

The connection to the end of the boom, is b means of two pins 25 and 26, at right ang es to one another with a yoke between them, as shown in Fig. 5, so that perfect freedom of motion is secured and the bucket may swing as a pendulum, either sideways or fore and aft while at the same time preserving the necessary rigidity for forcing it into the material to be excavated.

27 is a member sliding telescopically within the member24. -Its purpose is to maintain the shells 2121 in position, and to provide an attachment for the closing rope 28, whichis attached to the u per end. The members 24 and 27 may be tu ular, or in the form of hollow boxgirders, or any other preferred construction, so. long as one can slide within or upon the other.

UAt the upper end of the member 24 is a sheave 29 over which a rope or chain 28 for closing the bucket by power is made to pass. Th1s closing rope orchain is carried within the boom to a cylinder 31, which is firmly fixed in suitable osition and moves with the boom. This cylinder is single acting only, its function being to pull upon the rope 28 thereby raising the member 27 after the bucket is in contact with the the shells 21-21 to powerfully an gather up .a load of premure of the apparatus is exerted tov cause the cutting edges of the bucket to penetrate the ground through the medium of the links 23 and the rigid member 24.

It is apparent that when the bucket is lifted with its a load to the high. position shown by dotted lines, and 'upon releasing the tension of the" closing rope of cylinder 31, the weight ofthe apparatus and the will cause it to open byweight of the material within the bucket gravity, and dump the load, as is'the usua operation of the clamshell buckets operated on the two line principle. It will be seen however, that my system of. applying closing power to the bucket is essentially difierent' from that usually employed because no multiplying sheaves, or closing wheels or gearing are employed -within the bucket. [There are 'many forms of such closing gear in use, and they are necessary as long asthe bucket is suspended by a flexible tackle. But they are entirely eliminatedby the use of my invention. L

The centre of gravity ofthe rolling cantilever is preferably fixed at a point below the wristin 20, for an important reason about to e described; If the center of gravity of the whole rolling apparatus were fixed to coincide with the wrist-pin 20, it would be in equilibrium in any and all positions to 'whlch it may roll upon the track. The center orgravity, however being below this point causes it to balance-only in mid-position and ,toexert a ri hting moment both above and below the mid-position, the action being similar to that or a rocking chair upon thefioor.

The hull. is moored in lace, either by spuds or mooring lines and anchorages, or both in any usual or preferred way.

The mach'ne, is controll d a suitable valves and coacting parts which w m it steam or compressed air to and from the cylinders,

andthe control levers for the operator will or may be arranged in convenient position upon the turntable. Either steam orcom-' pressed air may be used as preferred,'and thesupply pi as may be carried up through the center 0 the turntable with any preferred arrangement of swivel or flexible joints.

Having thus described-the construction of the maehme, the action is now clear. Upon the admission of .steam or our to the c linder 15, the clamshell bucket is pre own in an open position on the ground, to be lit) excavated, and air is then admitted to cylinder 3l, whereupon the closing action takes place and the bucket is filled. Immediately thereafter the pressure from cylinder 15 being relieved, the bucket begins to rise of its own accord, due to the righting moment and the energy which has been stored up in the apparatus durin thedown stroke. All that the cylinder 15 as to {do therefore is to accelerate and control the stroke, carrying it past the. neutral or mid-position, partly by means of, its momentum, and partly by the additional energy" imparted to it untilJ -the proper height is reached. During thejlifting operation, the slewing or revolving of the boom has been put into efiect, so that by the time it has reached the top it isjin proper positionto dump the load, the pressure on cylinder 31'is then released, and the bucket opens by gravity, and dumps the load upon which the slewing and descending motion is recommenced.

It will be seen therefore that the power I applied to the apparatus'is comparatively small, and' that great economy thereby results.

I amaware that the construction of a clamshell bucket and its essential parts,

old and well known, and I- do not confine rolling cantilever upon a revolving platform as stated, and with the described coacting mechanism constructed and arranged for the purpose described is anew and useful improvement .in dredges ,ot the class stated. Also the turntable mounted-on a live roller ring is a well known device, and has many use u l applications. l do not therefore broadly claim these details orelements as heretofore used. I a

Itwill be obvious-to those who are lamiliar with such matters that modifications other than those illustrated and described maybe adopted, and yet the essentials of the invention be retained. lltheretore do not limit mysell to such details. There are many minor and supplemental devices coni nected with this operation which may be beneficially used, as for instance, a brake or attachment for holding the boom in anyposition.

l claim: 8 1. line dredge, a balanced boom member having a rolling surface on its lower side formed in an arc of a circle and having the center of gravity located below the center of said are so that the boom. member is in.

equilibrium when in mid-position. I a

2. In a dredge, a-balanced rolling boom member having a convex rolling surface on J its lower side formed in an arc of a circle and having the center of gravity below the center of said are so that the boom member is in equillbriumwhen inmid-position, teeth nectionat the center of the arc whic moves j in a horizontallme and power devices connected to said pin.

4..,In a dredge, anormally balanced. roll-z ing cantilever boom having-a. convex rolling us I on said rolling surface and a track with teeth 7 rolling surface in an arc of a circle, a track for said surface, a counterweight at the inner end 0 said boom and a ortion at the outer end curved to extend be ow the track when the parts are in normally balanced position. 5. In a dredge, a normally balanced rollin cantilever boom having convex toothed ro ling surfaces, a track for the rolling surfaces, a clamshell bucket attached to the outer end of the boom, and means to actuate the boom.

6. In a dredge, a balanced rolling cantilever boom havmg a convex rolling surface in an arc of a circle, a wrist pin at the center of the arc of the rolling cantilever boom which moves in a horizontal line, a direct acting cylinder and a iston rod in said cylinder directly attached to the wrist pin.

.7. A balanced rolling cantileverboom hav- I ingco'nvex rolling surfaces in the arc of a circle, a track for the rolling surfaces, and means to actuate the boom supported on and moved with it the center of gravity of the boom lyin substantially directly below the center of t e are of the circle when the parts are in normal mid-position whereby the boom tends to return to this position when moved away therefrom in either direction.

8. A rocking cantilever boom havin convex rolling surfaces on an arc of a circ e and having a shifting point of support beneath and on both sides of the center of gravity of said boom, a track for the rolling surfaces, a revolving turntable under said track, and means for im arting rolling movement to said boom an turntable.

ARTHUR WELLS ROBINSON. 

